In recent years, a liquid immersion lithography process has been reported as a new lithography technique (see Non-patent Document 1 to 3). In this method, a resist film is exposed to form a resist pattern in a state where a liquid immersion medium having a predetermined thickness is interposed on at least the resist film in an exposure light path between an exposure device (lens) and the resist film on a substrate upon exposure.
Air or an inert gas such as nitrogen has been interposed in a conventional exposure light path space, but in this liquid immersion lithography process, the gas in the exposure light path space is replaced with the liquid immersion medium (e.g., pure water and fluorine-based inert liquids) having a refractive index (n) which is larger than that of the gas and is smaller than that of the resist film. Thereby, the liquid immersion lithography process has an advantage that even though a light source having a wavelength for the exposure conventionally used is employed, high resolution can be achieved without lowering the focal depth width like the case where a light source having a shorter wavelength or a lens having a higher NA is used.
By using a resist composition for such a liquid immersion lithography process and the lens mounted in the existing exposure device, it is possible to form the resist patter having a higher resolution and an excellent focal depth with low cost (see Patent Document 1).
Also a technology which aims at simultaneously preventing an alteration of the resist film due to the liquid immersion medium and a variation of the refractive index associated with the alteration of the liquid immersion medium due to an elution component from the resist film by forming a resist protection film on the resist film using a fluorine-containing resin which can be dissolved only in a particular solvent and interposing the liquid immersion medium on this resist protection film has been proposed (see Patent Document 2)
More recently, from viewpoints of simplifying a resist pattern formation process and enhancing a production efficiency, a technology in which by using the resist protection film which is alkali-soluble, removal of the resist protection film and the formation of the resist pattern are performed simultaneously upon alkali development after the liquid immersion exposure has been proposed (see Patent Document 3).    Non-Patent Document 1: Journal of Vacuum Science & Technology B (Published in U.S.A.), Vol. 17, No. 6, pp. 3306-3309, 1999.    Non-Patent Document 2: Journal of Vacuum Science & Technology B (Published in U.S.A.), Vol. 19, No. 6, pp. 2353-2356, 2001.    Non-Patent Document 3: Proceedings of SPIE (Published in U.S.A.), Vol. 4691, pp. 459-465, 2002.    Patent Document 1: PCT International Publication No. WO 2004/068242    Patent Document 2: PCT International Publication No. WO 2004/074937    Patent Document 3: Japanese Unexamined Patent Application, Publication No. 2005-264131